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SYSLOGD(8) BSD System Manager's Manual SYSLOGD(8)
NAMEsyslogd -- log systems messages
SYNOPSISsyslogd [-468ACcdFHkNnosTuv] [-aallowed_peer] [-bbind_address]
[-fconfig_file] [-l [mode:]path] [-mmark_interval] [-Oformat]
[-Ppid_file] [-plog_socket] [-Slogpriv_socket]
DESCRIPTION
The syslogd utility reads and logs messages to the system console, log
files, other machines and/or users as specified by its configuration
file.
The options are as follows:
-4 Force syslogd to use IPv4 addresses only.
-6 Force syslogd to use IPv6 addresses only.
-8 Tells syslogd not to interfere with 8-bit data. Normally syslogd
will replace C1 control characters (ISO 8859 and Unicode
characters) with their "M-x" equivalent. Note, this option does
not change the way syslogd alters control characters (see
iscntrl(3)). They will always be replaced with their "^x" equiv-
alent.
-A Ordinarily, syslogd tries to send the message to only one address
even if the host has more than one A or AAAA record. If this op-
tion is specified, syslogd tries to send the message to all ad-
dresses.
-aallowed_peer
Allow allowed_peer to log to this syslogd using UDP datagrams.
Multiple -a options may be specified.
The allowed_peer option may be any of the following:
ipaddr[/masklen][:service]
Accept[datagramsnfrome_i_p_a_d_d<i>r,
ipaddr can be specified as an
IPv4 address or as an IPv6 ad-
dress enclosed with `[' and `]'.
If specified, service is the name
or number of an UDP service (see
services(5)) the source packet
must belong to. A service of `*'
accepts UDP packets from any
source port. The default service
is `syslog'. If ipaddr is IPv4
address, a missing masklen will
be substituted by the historic
class A or class B netmasks if
ipaddr belongs into the address
range of class A or B, respec-
tively, or by 24 otherwise. If
ipaddr is IPv6 address, a missing
masklen will be substituted by
128.
domainname[:service] Accept datagrams where the re-
verse address lookup yields
domainname for the sender ad-
dress. The meaning of service is
as explained above. domainname
can contain special characters of
a shell-style pattern such as
`*'.
The -a options are ignored if the -s option is also specified.
-bbind_address[:service]
-b :service
Bind to a specific address and/or port. The address can be spec-
ified as a hostname, and the port as a service name. If an IPv6
address is specified, it should be enclosed with `[' and `]'.
The default service is `syslog'. This option can be specified
multiple times to bind to multiple addresses and/or ports.
-C Create log files that do not exist (permission is set to `0600').
-c Disable the compression of repeated instances of the same line
into a single line of the form "last message repeated N times"
when the output is a pipe to another program. If specified
twice, disable this compression in all cases.
-d Put syslogd into debugging mode. This is probably only of use to
developers working on syslogd.
-fconfig_file
Specify the pathname of an alternate configuration file; the de-
fault is /etc/syslog.conf.
-F Run syslogd in the foreground, rather than going into daemon
mode. This is useful if some other process uses fork(2) and
exec(3) to run syslogd, and wants to monitor when and how it ex-
its.
-H When logging remote messages use hostname from the message (if
supplied) instead of using address from which the message was re-
ceived.
-k Disable the translation of messages received with facility "kern"
to facility "user". Usually the "kern" facility is reserved for
messages read directly from /dev/klog.
-mmark_interval
Select the number of minutes between "mark" messages; the default
is 20 minutes.
-N Disable binding on UDP sockets. RFC 3164 recommends that outgo-
ing syslogd messages should originate from the privileged port,
this option disables the recommended behavior. This option in-
herits -s.
-n Disable DNS query for every request.
-Oformat
Select the output format of generated log messages. The values
bsd and rfc3164 are used to generate RFC 3164 log messages. The
values syslog and rfc5424 are used to generate RFC 5424 log mes-
sages, having RFC 3339 timestamps with microsecond precision.
The default is to generate RFC 3164 log messages.
-o Prefix kernel messages with the full kernel boot file as deter-
mined by getbootfile(3). Without this, the kernel message prefix
is always "kernel:".
-plog_socket
Specify the pathname of an alternate log socket to be used in-
stead; the default is /var/run/log. When a single -p option is
specified, the default pathname is replaced with the specified
one. When two or more -p options are specified, the remaining
pathnames are treated as additional log sockets.
-Ppid_file
Specify an alternative file in which to store the process ID.
The default is /var/run/syslog.pid.
-Slogpriv_socket
Specify the pathname of an alternate log socket for privileged
applications to be used instead; the default is /var/run/logpriv.
When a single -S option is specified, the default pathname is re-
placed with the specified one. When two or more -S options are
specified, the remaining pathnames are treated as additional log
sockets.
-l [mode:]path
Specify a location where syslogd should place an additional log
socket. The primary use for this is to place additional log
sockets in /var/run/log of various chroot filespaces. File per-
missions for socket can be specified in octal representation in
mode, delimited with a colon. The socket location must be speci-
fied as an absolute pathname in path.
-s Operate in secure mode. Do not log messages from remote ma-
chines. If specified twice, no network socket will be opened at
all, which also disables logging to remote machines.
-T Always use the local time and date for messages received from the
network, instead of the timestamp field supplied in the message
by the remote host. This is useful if some of the originating
hosts cannot keep time properly or are unable to generate a cor-
rect timestamp.
-u Unique priority logging. Only log messages at the specified pri-
ority. Without this option, messages at the stated priority or
higher are logged. This option changes the default comparison
from "=>" to "=".
-v Verbose logging. If specified once, the numeric facility and
priority are logged with each locally-written message. If speci-
fied more than once, the names of the facility and priority are
logged with each locally-written message.
This option only affects the formatting of RFC 3164 messages.
Messages formatted according to RFC 5424 always include a facil-
ity/priority number.
The syslogd utility reads its configuration file when it starts up and
whenever it receives a hangup signal. For information on the format of
the configuration file, see syslog.conf(5).
The syslogd utility reads messages from the UNIX domain sockets
/var/run/log and /var/run/logpriv, from an Internet domain socket speci-
fied in /etc/services, and from the special device /dev/klog (to read
kernel messages).
The syslogd utility creates its process ID file, by default
/var/run/syslog.pid, and stores its process ID there. This can be used
to kill or reconfigure syslogd.
The message sent to syslogd should consist of a single line. The message
can contain a priority code, which should be a preceding decimal number
in angle braces, for example, `<5>'. This priority code should map into
the priorities defined in the include file <sys/syslog.h>.
For security reasons, syslogd will not append to log files that do not
exist (unless -C option is specified); therefore, they must be created
manually before running syslogd.
The date and time are taken from the received message. If the format of
the timestamp field is incorrect, time obtained from the local host is
used instead. This can be overridden by the -T flag.
FILES
/etc/syslog.conf configuration file
/var/run/syslog.pid default process ID file
/var/run/log name of the UNIX domain datagram log socket
/var/run/logpriv UNIX socket for privileged applications
/dev/klog kernel log device
SEE ALSOlogger(1), syslog(3), services(5), syslog.conf(5), newsyslog(8)HISTORY
The syslogd utility appeared in 4.3BSD.
The -a, -s, -u, and -v options are FreeBSD 2.2 extensions.
BUGS
The ability to log messages received in UDP packets is equivalent to an
unauthenticated remote disk-filling service, and should probably be dis-
abled by default. Some sort of inter-syslogd authentication mechanism
ought to be worked out. To prevent the worst abuse, use of the -a option
is therefore highly recommended.
The -a matching algorithm does not pretend to be very efficient; use of
numeric IP addresses is faster than domain name comparison. Since the
allowed peer list is being walked linearly, peer groups where frequent
messages are being anticipated from should be put early into the -a list.
The log socket was moved from /dev to ease the use of a read-only root
file system. This may confuse some old binaries so that a symbolic link
might be used for a transitional period.
BSD July 2, 2018 BSD